We found that 3-amino-1,2,4-triazole (AT) is a cataractogenic agent. The morphology of AT-cataract is somewhat similar to that observed in senile cataract. Our observations of the production of cataract by AT, a specific inhibitor of catalase, and the increased levels of H2O2 in eye humors with a simultaneous decrease in catalase activity of lens capsule-epithelium and unaltered GSH-peroxidase activity and GSH content of lens after a single intravenous injection of AT in the rabbit, indicate the significance of catalase in the regulation of H2O2 in eye humors and possibly in the lens. Our main objective is to investigate the relative roles of catalase and GSH- peroxidase in regulation of H2O2 in the eye. Assay of catalase will be done polarographically using a Clark electrode and that of GSH- peroxidase by a spectrophotometric technique. To confirm the source of H2O2 in eye humors, the effects of AT on ascorbic acid in lens and aqueous and viterous humor, and on the enzymes producing H2O2 in surrounding tissues will be observed. It is possible that the increased H2O2 in eye humors that we observed after AT injection may cause oxidative damage to the cells in lens and thus can result in cataract production. The studies proposed here to explore the effect of ATon membrane transport and synthesis of protein and ATP are of significance in understanding the role of endogenous peroxide in cataractogenesis. Rabbit lenses will be exposed to AT, in vivo and in vitro, with and without ultraviolet irradiation. We intend to use the following radioactive probes to determine the effects of AT: Rb86 and Na24 to evaluate cation transport, C14-leucine to study protein synthesis, Pi32 incorporation to investigate synthesis of ATP, alpha- AlB, C14-deoxyglucose to examine mediated transport, and C14-thiourea as a substance which undergoes simple diffusion in the lens. We also propose to study the effect of AT, in vivo and in vitro, on the lenses of acatalasemic mice which belong to a genetic strain deficient in catalase.